Splice variants of a ClC-2 chloride channel with differing functional characteristics

We identified two ClC-2 clones in a guinea pig intestinal epithelial cDNA l ibrary, one of which carries a 30-bp deletion in the NH2 terminus. PCR usin g primers encompassing the deletion gave two products that furthermore were amplified with specific primers confirming their authenticity. The corresp onding genomic DNA sequence gave a structure of three exons and two introns . An internal donor site occurring within one of the exons accounts for the deletion, consistent with alternative splicing. Expression of the variants gpClC-2 and gpClC-2 Delta 77-86 in HEK-293 cells generated inwardly rectif ying chloride currents with similar activation characteristics. Deactivatio n, however, occurred with faster kinetics in gpClC-2 Delta 77-86. Site-dire cted mutagenesis suggests that a protein kinase C-mediated phosphorylation consensus site lost in gpClC-2 Delta 77-86 is not responsible for the obser ved change. The deletion-carrying variant is found in most tissues examined , and it appears more abundant in proximal colon, kidney, and testis. The p resence of a splice variant of ClC-2 modified in its NH2-terminal domain co uld have functional consequences in tissues where their relative expression levels are different.